Sulfur distribution at the semiconductor-XLPE interfaces of HV cables

The concentration profile of sulfur in the semiconductor and insulation of XLPE HV cables has been measured using scanning micro-PIXE and NAA (Neutron Activation Analysis). Data collected at 25 and 50 μm spacing adjacent to the semiconductor-XLPE interfaces (in the first 500 microns) showed a 25% to 40% decrease in sulfur relative to the concentration in the bulk XLPE. Sulfur was the only impurity to exhibit this concentration decrease in terms of the radial position, for both virgin and electrically aged samples. Since the most probable source of the observed sulfur is the antioxidant added to the resin, micro-scanning FTIR measurements were also performed. The absorbance at 3510 cm^-1 in terms of the radial position is presented